/* Write some buf1 data to pty, processing IACs.
* Update wridx1 and size1. Return < 0 on error.
* Buggy if IAC is present but incomplete: skips them.
*/
static ssize_t
safe_write_to_pty_decode_iac(struct tsession *ts)
{
unsigned wr;
ssize_t rc;
unsigned char *buf;
unsigned char *found;
buf = TS_BUF1(ts) + ts->wridx1;
wr = MIN(BUFSIZE - ts->wridx1, ts->size1);
/* wr is at least 1 here */
if (ts->buffered_IAC_for_pty) {
/* Last time we stopped on a "dangling" IAC byte.
* We removed it from the buffer back then.
* Now pretend it's still there, and jump to IAC processing.
*/
ts->buffered_IAC_for_pty = 0;
wr++;
ts->size1++;
buf--; /* Yes, this can point before the buffer. It's ok */
ts->wridx1--;
goto handle_iac;
}
found = memchr(buf, IAC, wr);
if (found != buf) {
/* There is a "prefix" of non-IAC chars.
* Write only them, and return.
*/
if (found)
wr = found - buf;
/* We map \r\n ==> \r for pragmatic reasons:
* many client implementations send \r\n when
* the user hits the CarriageReturn key.
* See RFC 1123 3.3.1 Telnet End-of-Line Convention.
*/
rc = wr;
found = memchr(buf, '\r', wr);
if (found)
rc = found - buf + 1;
rc = safe_write(ts->ptyfd, buf, rc);
if (rc <= 0)
return rc;
if (rc < wr /* don't look past available data */
&& buf[rc-1] == '\r' /* need this: imagine that write was _short_ */
&& (buf[rc] == '\n' || buf[rc] == '\0')
) {
rc++;
}
goto update_and_return;
}
/* buf starts with IAC char. Process that sequence.
* Example: we get this from our own (bbox) telnet client:
* read(5, "\377\374\1""\377\373\37""\377\372\37\0\262\0@\377\360""\377\375\1""\377\375\3"):
* IAC WONT ECHO, IAC WILL NAWS, IAC SB NAWS <cols> <rows> IAC SE, IAC DO SGA
* Another example (telnet-0.17 from old-netkit):
* read(4, "\377\375\3""\377\373\30""\377\373\37""\377\373 ""\377\373!""\377\373\"""\377\373'"
* "\377\375\5""\377\373#""\377\374\1""\377\372\37\0\257\0I\377\360""\377\375\1"):
* IAC DO SGA, IAC WILL TTYPE, IAC WILL NAWS, IAC WILL TSPEED, IAC WILL LFLOW, IAC WILL LINEMODE, IAC WILL NEW_ENVIRON,
* IAC DO STATUS, IAC WILL XDISPLOC, IAC WONT ECHO, IAC SB NAWS <cols> <rows> IAC SE, IAC DO ECHO
*/
if (wr <= 1) {
/* Only the single IAC byte is in the buffer, eat it
* and set a flag "process the rest of the sequence
* next time we are here".
*/
//bb_error_msg("dangling IAC!");
ts->buffered_IAC_for_pty = 1;
rc = 1;
goto update_and_return;
}
handle_iac:
/* 2-byte commands (240..250 and 255):
* IAC IAC (255) Literal 255. Supported.
* IAC SE (240) End of subnegotiation. Treated as NOP.
* IAC NOP (241) NOP. Supported.
* IAC BRK (243) Break. Like serial line break. TODO via tcsendbreak()?
* IAC AYT (246) Are you there. Send back evidence that AYT was seen. TODO (send NOP back)?
* These don't look useful:
* IAC DM (242) Data mark. What is this?
* IAC IP (244) Suspend, interrupt or abort the process. (Ancient cousin of ^C).
* IAC AO (245) Abort output. "You can continue running, but do not send me the output".
* IAC EC (247) Erase character. The receiver should delete the last received char.
* IAC EL (248) Erase line. The receiver should delete everything up tp last newline.
* IAC GA (249) Go ahead. For half-duplex lines: "now you talk".
* Implemented only as part of NAWS:
* IAC SB (250) Subnegotiation of an option follows.
*/
if (buf[1] == IAC) {
/* Literal 255 (emacs M-DEL) */
//bb_error_msg("255!");
rc = safe_write(ts->ptyfd, &buf[1], 1);
/*
* If we went through buffered_IAC_for_pty==1 path,
* bailing out on error like below messes up the buffer.
* EAGAIN is highly unlikely here, other errors will be
* repeated on next write, let's just skip error check.
*/
#if 0
if (rc <= 0)
return rc;
#endif
rc = 2;
goto update_and_return;
}
if (buf[1] >= 240 && buf[1] <= 249) {
/* NOP (241). Ignore (putty keepalive, etc) */
/* All other 2-byte commands also treated as NOPs here */
rc = 2;
goto update_and_return;
}
if (wr <= 2) {
/* BUG: only 2 bytes of the IAC is in the buffer, we just eat them.
* This is not a practical problem since >2 byte IACs are seen only
* in initial negotiation, when buffer is empty
*/
rc = 2;
goto update_and_return;
}
if (buf[1] == SB) {
if (buf[2] == TELOPT_NAWS) {
/* IAC SB, TELOPT_NAWS, 4-byte, IAC SE */
struct winsize ws;
if (wr <= 6) {
/* BUG: incomplete, can't process */
rc = wr;
goto update_and_return;
}
memset(&ws, 0, sizeof(ws)); /* pixel sizes are set to 0 */
ws.ws_col = (buf[3] << 8) | buf[4];
ws.ws_row = (buf[5] << 8) | buf[6];
ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws);
rc = 7;
/* trailing IAC SE will be eaten separately, as 2-byte NOP */
goto update_and_return;
}
/* else: other subnegs not supported yet */
}
/* Assume it is a 3-byte WILL/WONT/DO/DONT 251..254 command and skip it */
#if DEBUG
fprintf(stderr, "Ignoring IAC %s,%s\n",
TELCMD(buf[1]), TELOPT(buf[2]));
#endif
rc = 3;
update_and_return:
ts->wridx1 += rc;
if (ts->wridx1 >= BUFSIZE) /* actually == BUFSIZE */
ts->wridx1 = 0;
ts->size1 -= rc;
/*
* Hack. We cannot process IACs which wrap around buffer's end.
* Since properly fixing it requires writing bigger code,
* we rely instead on this code making it virtually impossible
* to have wrapped IAC (people don't type at 2k/second).
* It also allows for bigger reads in common case.
*/
if (ts->size1 == 0) { /* very typical */
//bb_error_msg("zero size1");
ts->rdidx1 = 0;
ts->wridx1 = 0;
return rc;
}
wr = ts->wridx1;
if (wr != 0 && wr < ts->rdidx1) {
/* Buffer is not wrapped yet.
* We can easily move it to the beginning.
*/
//bb_error_msg("moved %d", wr);
memmove(TS_BUF1(ts), TS_BUF1(ts) + wr, ts->size1);
ts->rdidx1 -= wr;
ts->wridx1 = 0;
}
return rc;
}
/*
Remove all IAC's from buf1 (received IACs are ignored and must be removed
so as to not be interpreted by the terminal). Make an uninterrupted
string of characters fit for the terminal. Do this by packing
all characters meant for the terminal sequentially towards the end of buf.
Return a pointer to the beginning of the characters meant for the terminal
and make *num_totty the number of characters that should be sent to
the terminal.
Note - if an IAC (3 byte quantity) starts before (bf + len) but extends
past (bf + len) then that IAC will be left unprocessed and *processed
will be less than len.
CR-LF ->'s CR mapping is also done here, for convenience.
NB: may fail to remove iacs which wrap around buffer!
*/
static unsigned char *
remove_iacs(struct tsession *ts, int *pnum_totty)
{
unsigned char *ptr0 = TS_BUF1(ts) + ts->wridx1;
unsigned char *ptr = ptr0;
unsigned char *totty = ptr;
unsigned char *end = ptr + MIN(BUFSIZE - ts->wridx1, ts->size1);
int num_totty;
while (ptr < end) {
if (*ptr != IAC) {
char c = *ptr;
*totty++ = c;
ptr++;
/* We map \r\n ==> \r for pragmatic reasons.
* Many client implementations send \r\n when
* the user hits the CarriageReturn key.
* See RFC 1123 3.3.1 Telnet End-of-Line Convention.
*/
if (c == '\r' && ptr < end && (*ptr == '\n' || *ptr == '\0'))
ptr++;
continue;
}
if ((ptr+1) >= end)
break;
if (ptr[1] == NOP) { /* Ignore? (putty keepalive, etc.) */
ptr += 2;
continue;
}
if (ptr[1] == IAC) { /* Literal IAC? (emacs M-DEL) */
*totty++ = ptr[1];
ptr += 2;
continue;
}
/*
* TELOPT_NAWS support!
*/
if ((ptr+2) >= end) {
/* Only the beginning of the IAC is in the
buffer we were asked to process, we can't
process this char */
break;
}
/*
* IAC -> SB -> TELOPT_NAWS -> 4-byte -> IAC -> SE
*/
if (ptr[1] == SB && ptr[2] == TELOPT_NAWS) {
struct winsize ws;
if ((ptr+8) >= end)
break; /* incomplete, can't process */
ws.ws_col = (ptr[3] << 8) | ptr[4];
ws.ws_row = (ptr[5] << 8) | ptr[6];
ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws);
ptr += 9;
continue;
}
/* skip 3-byte IAC non-SB cmd */
#if DEBUG
fprintf(stderr, "Ignoring IAC %s,%s\n",
TELCMD(ptr[1]), TELOPT(ptr[2]));
#endif
ptr += 3;
}
num_totty = totty - ptr0;
*pnum_totty = num_totty;
/* The difference between ptr and totty is number of iacs
we removed from the stream. Adjust buf1 accordingly */
if ((ptr - totty) == 0) /* 99.999% of cases */
return ptr0;
ts->wridx1 += ptr - totty;
ts->size1 -= ptr - totty;
/* Move chars meant for the terminal towards the end of the buffer */
return memmove(ptr - num_totty, ptr0, num_totty);
}
